LNG custody transfer measurement and quantity verification.
LNG custody transfer determines the quantity of product that changes commercial ownership at the ship/shore interface. The measurement establishes the invoicing quantity and forms the primary evidence in settlement disputes. FUTUREGAZ supports the full custody transfer process, from transfer point meter review through to GIIGNL-method quantity calculation and independent crosscheck against ship and shore figures.
At LNG terminals and FSRUs, custody transfer occurs at the ship/shore interface during loading or unloading. The quantity is determined from tank level measurements, density calculations, and flow metering, with the GIIGNL Custody Transfer Handbook providing the principal method reference. Small errors in density or calorific value inputs scale directly with cargo volume and can represent material commercial exposure.
FUTUREGAZ provides independent review of the measurement basis, calculation method, and supporting documentation. The work is structured to identify deviations from the GIIGNL method, assess calibration status of instruments involved in the transfer, and produce a documented position that can be used in settlement or regulatory reporting.
What this covers
Ship's figure review
Review of LNG vessel quantity determination including tank level measurement, temperature correction, density calculation, and ship's quantity figure against the GIIGNL method.
Shore figure reconciliation
Independent calculation of shore-side quantity from flow metering or shore tank measurements, and reconciliation against the ship figure to identify and explain differences.
Density and calorific value
Review of sampled composition data, density determination method, and calorific value calculation against ISO 6976, including sample representativeness and chromatograph calibration status.
BOG accounting
Assessment of boil-off gas accounting during loading and unloading, including vapour return flow metering, heel estimation, and consistency with the transfer period timeline.
GIIGNL method application
Verification that all steps of the GIIGNL Custody Transfer Handbook method have been correctly applied, including the specified corrections, reference conditions, and calculation sequence.
Transfer point meter verification
Review of ultrasonic and Coriolis meter calibration records, most recent proving results, and compliance with the applicable standard and contractual measurement basis.
Applicable standards and references
GIIGNL Custody Transfer Handbook
The primary international reference for LNG quantity determination at ship/shore transfer points. Covers tank measurement, density, calorific value, BOG, and quantity reconciliation.
Calorific value determination
Standard for calculating calorific value, density, and relative density of natural gas and other gaseous fuels from composition data.
Turbine and ultrasonic metering
American Gas Association standard for measurement of natural gas by turbine meters, referenced for LNG vapour metering applications.
Ultrasonic flow measurement
AGA standard for measurement of gas by multipath ultrasonic meters, applied at LNG regasification and vaporisation metering points.
Measuring systems for LNG
OIML recommendation for measuring systems used in the dynamic measurement of cryogenic liquids including LNG.
Frequently asked questions
What is LNG custody transfer?
LNG custody transfer is the process of determining the quantity of liquefied natural gas that changes ownership at the ship/shore interface during loading or unloading. The measurement establishes the contractual quantity for invoicing and is the primary reference in any subsequent commercial dispute.
What are ship's and shore figures?
The ship's figure is the LNG quantity calculated from the vessel's measurement systems, including tank level gauges, temperature sensors, and density determination. The shore figure is calculated from land-based instruments at the terminal. Both are calculated independently and then reconciled. Differences are investigated and allocated according to the contractual measurement basis.
Why do LNG quantity disputes arise?
Disputes arise most often from differences in density determination methodology, inconsistent application of the GIIGNL method between parties, timing differences in tank measurement, calibration divergence between ship and shore instruments, or unresolved questions about BOG accounting during the transfer period.
What is the GIIGNL Custody Transfer Handbook?
The GIIGNL Custody Transfer Handbook is published by the International Group of Liquefied Natural Gas Importers and sets out the standard methodology for LNG quantity determination at ship/shore transfer points. It is the principal technical reference for LNG custody transfer calculations globally.
When is independent measurement verification needed?
Independent verification is useful before signing long-term supply or terminal agreements, when a transfer dispute has arisen or is anticipated, following instrument replacement or recalibration at a transfer point, and as a routine quality check on the measurement methodology being applied.
Discuss a custody transfer measurement requirement.
Describe the terminal type, transfer point, and measurement basis. We will respond with an appropriate approach.
Send an enquiry contact@futuregaz.com